Resistance contactor



Nov. 8, 1938. H. F. FRUTH RESISTANCE CONTACT-OR Filed April 22, 1937 k m a H ATTORNEY Patented Nov. 8, 1938 UNITED STATES PATENT OFFICE Hal F. Fruth, Riverside, Ill., assignor to P. R.

Mallory & 00., Inc., Indianapolis, Ind., a corporation of Delaware Application April 22, 1937, Serial No. 138,336

9 Claims.

This invention relates to variable resistance devices and particularly for contactors therefor.

The present applicationcomprisesa continuation in part'of my copending applications Serial Number 13,239, filed March 27, 1935, and Serial Number 68,870, filed March 14, 1936.

An object of the invention is to improve a variable resistance device.

Another object is to improve the contact arrangement therefor.

Other objects of the invention will be apparent from the following description and accompanying drawing taken in connection with the appended claims.

The invention comprises the features of construction, combination of elements, arrangement of parts, and methods of manufacture and operation referred to above or which will be brought out-an'd exemplified in the disclosure hereinafter set forth, including the illustrations in the drawing.

In the drawing:

Figure 1 is a face View of a variable resistance device with the cover removed;

Figure 2 is a section on the line 2--2 of Figure 1 with the cover added;

Figure 3 is a perspective view of the contactor for said device;

Figure 4 shows the contactor and contact arm assembly in perspective;

Figure 5 is a section on the line 5-5 of Figure 4;

Figure 6 shows a modified contactor;

Figure 7 shows a modified mounting for said contactor; and

Figure 8 is a section on the line 8-8 of Figure 7.

The invention contemplates a novel form of cylindrical contactor for a variable resistance device and a novel method of mounting the same.

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the method of procedure and the construction of parts with out departing from the spirit of the invention. In the following description and in the claims,

' parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

Referring to the drawing the variable resistance device comprises a base- 20 upon which is mounted a ring 2| of suitable insulating material, such as Bakelite, resin impregnated fibre, jelled oil impregnated fibre or the like. A resistance layer 22 is disposed on the upper face of ring 2|.

Layer 22 may be of any suitable composition such as finely divided carbon, graphite or other conductive material suspended in shellac or other binder material.

Terminal layers 23 and 24 of silver paint, 5

sprayed metal or the like are deposited on top of resistance layer 22 to furnish low resistance connections to the terminal lugs 25 and 26.

The moving contacting structure comprises a shaft 21, a' contact arm 28 secured to the end 10 of said shaft by means of an intermediate block 29 of sheet insulation. A terminal is provided for arm 28 through metal ring terminal 30. Arm 28 makes sliding contact with ring 30 through spring fingers 3 l 15 slightly longer than'the contactor 32 and some- What narrower than the diameter of the contactor. The two sides of the opening are formed to provide opposed projections 34 and 35. Contactor 32 is disposed in opening 33 with its cylindrical sides resting against projections 34 and 35 and against resistance surface 22 with its axis parallel to the resistance surface and transverse 30 to the direction of motion of the contactor during rotation of the contact arm.

It will be noted that projections 34 and 35 provide a pivotal engagement with contactor 32 so that it may rock on the contact arm and thereby 35 adapt itself to any irregularities in the resistance surface.

This contact arrangement is very economical to manufacture since it can be made from stock materials with a few simple operations. The contactor 32 can be cut from a length of round rod and the corners and surfaces rounded and smoothed by simple burnishing operations. It is noteworthy that no special dies are required and no machining is necessary.

The contact arm 28 can be stamped from stock sheet metal in a single machine operation.

Figure 6 shows a modified form of contactor 42 which is tubular in form and may. be pro-' duced by cutting from a length of metal tubing and burnishing as already described.

Figures 7 and 8 illustrate this contactor mounted in a modified contact arm 48 having an opening 43 of rectangular shape and of the length of the contactor and somewhat narrower 55 than the diameter of the contactor. A pair of ears 44 and 45 are turned down at the ends of the opening 43 and serve to aid in holding the contactor. This form of contactor may be sufficiently flexible to adjust itself to the resistance surface without the provision of rocker projections 34 and 35 on the contact arm. However, contactor 42 may readily be used in arm 28. Also, in some instances, contactor 32 can be used in contact arm 48.

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. A variable resistance device comprising a relatively smooth resistance surface, a movable contact arm arranged so as to move over said surface, said arm comprising a portion of sheet material spaced from said surface and having an aperture therein, a pair of oppositely disposed projections on opposite edges of said aperture, and a cylindrical contactor disposed in said aperture with its cylindrical surface engaging said resistance surface and also engaging said projections whereby said contactor has sliding contact with said surface and rocking contact with said projections.

2. A variable resistance device Comprising a relatively smooth resistance surface, a movable contact arm arranged so as to move over said surface, said arm comprising a portion of sheet material spaced from said surface and having an aperture therein, a pair of oppositely dis- ,posed projections on opposite edges of said aperture, and a cylindrical contactor disposed in said aperture with its cylindrical surface engaging said resistance surface and also engaging said projections whereby said contactor has sliding contact with said surface and is adapted to rock on said projections about an axis transverse of the axis of said contactor.

3. A variable resistance device comprising a relatively plane resistance surface, a movable contact arm arranged so as to move over said surface in spaced relation thereto, said arm comprising a portion of sheet material spaced from said surface and having an aperture therein, a pair of oppositely disposed projections on opposite edges of said aperture and in line with the direction of motion of said arm, and a cylindrical contactor disposed in said aperture with its cylindrical surface engaging said resistance surface and also engaging said projections whereby said contactor has sliding contact with said surface along a line transverse to its axis and rocking contact on said projections about an axis, parallel to said line.

4. A variable resistance device comprising a relatively plane arcuate resistance surface, a rotatable contact arm having its axis at the center of said arcuate surface, said arm comprising a sheet metal portion disposed in spaced relation to said resistance surface and substantially parallel thereto, said portion having an aperture therein above said resistance surface, said aperture being provided with opposing projections on the two sides thereof, the points of said projections being located in the same arc of travel of said contact arm, and a contactor member comprising a metal cylinder having its cylindrical surface engaging said resistance surcylindrical contactor held within said hole, said contactor having a diameter greater than the width of said hole and having its cylindrical surface engaging opposite edges of said-hole and also engaging said resistance surface.

6. A variable resistance device comprising a relatively smooth resistance surface, a movable contact member arranged'so as to move longitudinally over said surface, said member comprising a sheet of material spaced from said surface and having a hole cut therein and a cylindrical contactor held within said hole, said contactor having a diameter greater than the width of said hole and having its cylindrical surface engaging opposite edges of said hole and also engaging said resistance surface, the axis of said contactor being substantially parallel to said resistance surface and substantially perpendicular to its direction of motion over said surface.

7. A variable resistance device comprising a relatively smooth resistance surface, a movable contact member arranged so as to move longitudinally over said surface, said member comprising a sheet of metal spaced from said surface and substantially parallel thereto, said sheet having a substantially rectangular hole therein and a cylindrical contactor within said hole, said contactor having a diameter greater than the Width of said hole and having its cylindrical surface engaging opposite edges of said hole and also engaging said resistance surface, the axis of said contactor being substantially parallel to said resistance surface and substantially perpendicular to its direction of motion over said surface.

8. A-variable resistance device comprising a flat arcuate resistance surface, a rotatable contact arm pivoted adjacent said surface and having its free end arranged so as to move over said surface, said arm comprising a sheet of material spaced above said surface and parallel thereto, a hole in said sheet above said surface and a cylindrical contactor held within said hole, said contactor having a diameter greater than the width of said hole and having its cylindrical surface engaging opposite edges thereof and also engaging said resistance surface.

9. A variable resistance device comprising a flat arcuate resistance surface, a rotatable contact arm pivoted adjacent said surface and having its free end arranged so as to move over said surface, said arm comprising a sheet of material spaced above said surface and parallel thereto, a hole in said sheet above said surface and a cylindrical contactor held within said hole, said contactor having a diameter greater than the width of said hole and having its cylindrical surface engaging opposite edges thereof and also engaging said resistance surface, the axis of said contactor being substantially parallel to said resistance surface and substantially perpendicular to its direction of motion over said surface.

HAL F. FRU'I'H. 

